rattle from motor

[stroke.n.smoke]

A couple years ago I rebuilt my motor because it had a loud rattle at idle.  The bike still has the rattle at idle and its been two years.  It did need a rebuild as the crank bearings were not very smooth and the cylinder plating was peeled.  I got the cylinder replated and rebuilt the crank.  Do these bikes have a rattle at idle normally, once you rev it up slightly the rattle is none existant, but still worries me somewhat.  I am going to tear off the top end in the next couple months and have a look.  I rode with Snoopjon last fall and his bike rattles too, he figured his was louder than mine and I thought mine was louder but whatever, they both rattled.  Mine has a new motor.  Is this gear noise from the primary gears?  Or piston slap or bearing noise.  You can really hear it on video with the helmet cam, but like I said, it goes away quickly once revved up.  I had an old IT 465 that was this way too.  The motor runs strong still after two years and everyone says to not worry about it, but I do somewhat.  Mabye there is too much piston clearance, I used a wiseco and Max power replated the cylinder and fitted the piston.  I never actually measured anything before putting the motor back together, just trusted them...  I have run Amsoil Dominator oil at 40:1 for the last 4-5 years with zero issues but that rattle is annoying me to the point of another rebuild or something.  I have run everything from VP C12 and VP111 to pump gas and even Av gas with blends and octane boost/pump.  I have basically settled with AvGas LL100 octane (cheapest high octane) with 40:1 oil mixture.  Bike has run great.  I guess I will see what it looks like in a couple weeks when I tear it down, but if anyone has any ideas I would like to remedy the rattle while its apart.  I will be measuring up the piston and cylinder and checking the runout and crank clearances.


   

[ID KX500]

Mine does it too,,, somebody jump in here with an answer please,,, I don't think anything is wrong however.

[stroke.n.smoke]

I just did a quick search about the rattle and it seems that its normal.  I will have to talk with Snoopjon when he gets his back together and some hours on it.  Curious to see what it sounds like after his complete rebuild.

[stroke.n.smoke]

Have a listen to the rattle in this motor, I don't think I will even tear into mine to inspect anymore.  Mabye a compression test and look through the exhaust port.  Mabye a new head gasket, but other than that I think mine should be fine.  Mine sounds the same.

http://wolbrinkrace.blogspot.com/

[cbxracer30]

Just a guess but what about the clutch basket bearings on a CBX thats where all the motor noise comes from ?, pull the clutch in noise goes away .CBX

[RM_Rider14]

Had the same thing.  I have had this rattle on many different brands/models of 2-strokes.  99% of the time it's the two stupid 50mm rubber o-ring gaskets that go on the head pipe where it attaches to the cylinder.  I just put two new ones (and the copper crush washer/gasket thingy, may not see it, it gets flattened out) on my FMF pipe and the rattle is 100% gone now   Many people when they put an aftermarket pipe on forget to take these o-rings off the stock pipe and transfer them to the new pipe before putting it on the bike.  They also wear out and break every two years or so.  Take your head pipe off and see if yours are bad, or if they're even there for that matter.

  If you need to order them, part numbers;


50mm O-ring = 671E2550  (You need 2 of these)
Copper gasket = 11009-1949 (Only need one)

  It's amazing these three little pieces made the bike rattle free, and quiet

 Let me know what your outcome is....

[Friar-Tuck]

       
     I went back and read through the responses and apologize for not understanding.
    The KIPS sound is like a deep Diesel engine sound.
    The exhaust rattle is a higher pitched sound.   If you find the exhaust is the rattle your hearing, High temp RTV spread around the pipe sealing surface and wait 24hrs. before you ride.
  That will eliminate the free movement or rattle in the pipe.  The downside is I don't know for sure if it's worse on the pipe mounts or not.  I have not had any problems so far, however I did add some rubber to the pipe mounts trying to isolate some of the vibration but "your mileage may vary"
   You can replace the o'rings and crush washer more often and still keep the "free play"
  Just something else to consider....

 
    Tuck\o/

[matzilla]

The rattle is more than likely your KIPS valves muving vertically in their little spots. Mine does this also. Very normal for these bikes. They move just enough to annoy or embarass you. Not a problem though.

[ID KX500]

The rattle is more than likely your KIPS valves muving vertically in their little spots. Mine does this also. Very normal for these bikes. They move just enough to annoy or embarass you. Not a problem though.

I've had too many K5s to think it was bad,,,,good to know what it is,,,,,I thought it was the computer re-booting.   

[Polar-Bus]

A couple years ago I rebuilt my motor because it had a loud rattle at idle.  The bike still has the rattle at idle and its been two years.  It did need a rebuild as the crank bearings were not very smooth and the cylinder plating was peeled.  I got the cylinder replated and rebuilt the crank.  Do these bikes have a rattle at idle normally, once you rev it up slightly the rattle is none existant, but still worries me somewhat.  I am going to tear off the top end in the next couple months and have a look.  I rode with Snoopjon last fall and his bike rattles too, he figured his was louder than mine and I thought mine was louder but whatever, they both rattled.  Mine has a new motor.  Is this gear noise from the primary gears?  Or piston slap or bearing noise.  You can really hear it on video with the helmet cam, but like I said, it goes away quickly once revved up.  I had an old IT 465 that was this way too.  The motor runs strong still after two years and everyone says to not worry about it, but I do somewhat.  Mabye there is too much piston clearance, I used a wiseco and Max power replated the cylinder and fitted the piston.  I never actually measured anything before putting the motor back together, just trusted them...  I have run Amsoil Dominator oil at 40:1 for the last 4-5 years with zero issues but that rattle is annoying me to the point of another rebuild or something.  I have run everything from VP C12 and VP111 to pump gas and even Av gas with blends and octane boost/pump.  I have basically settled with AvGas LL100 octane (cheapest high octane) with 40:1 oil mixture.  Bike has run great.  I guess I will see what it looks like in a couple weeks when I tear it down, but if anyone has any ideas I would like to remedy the rattle while its apart.  I will be measuring up the piston and cylinder and checking the runout and crank clearances.


   

Also make sure you have the exhaust pipe o-rings and a good copper exhaust gasket (I like to use 2 gaskets) . 250/500cc  KX's exhaust header pipes often   vibrate against the inside bore of the cylinder.

[Johnniespeed]

I bought my K5 new, so I know what it is supposed to sound like. Whenever I hear a rattle in the "engine" it is always, always,always the exhaust mounting.  I just replace the gaskets ( I use two instead of one ) I replace the o-rings, and replace the broken mounts again and again.  Also if you do a search for the broken frame exhaust mount, you will find how others fix thier frame mount.
 Now maybe you do have an engine noise, but I wouldnt take anything apart until I knew for absolute sure the exhaust is perfectly mounted.
  I hope your noise is something simple and easy to fix, keep us posted.
 John

[RM_Rider14]

   

Also make sure you have the exhaust pipe o-rings and a good copper exhaust gasket (I like to use 2 gaskets) . 250/500cc  KX's exhaust header pipes often   vibrate against the inside bore of the cylinder.

  Four posts's up, did you read mine?  Great minds think alike

[stroke.n.smoke]

I did a compression test and its right at 180psi.  Looked into the exhaust port and everything looks great.  I don't think I will be pulling anything apart yet.  From all the response and the video's I am not going to worry about it.  One thing that does worry me somewhat, but after two years of running AV gas I am a little worried about things.  I have heard everything from (never run avgas, especially in a two stroke, the motor won't last long)  to (don't worry about it, it'll be fine).  I realize it has lead, but so does C12...  When I looked into the cylinder it was very clean, no piston wash on the top of the piston.  I did have the piston top coated by max power and the combustion chamber (actually they did the entire head)  It's very clean, the piston is real nice on the exhaust side when you roll it over too.  This is a Wiseco piston with a window in it.  I run the BR8EG and the timing plate is fully advanced, I also use the thinnest Kawi head gasket available.  40:1 Amsoil Dominator with 100 octane LowLead AVGAS for the last two years.  I ride at 1500 ft to 5000ft and weather from 0 degrees C to +30 degrees C.  I have never jetted for the elevation and weather, pretty much stock jetting, ya, it doesn't run perfect in all conditions but man, what a great bike.  I have a buddy with a new 200cc KTM XCW and he basically jets daily...   Just thought I would share that with you guys...

 

[snoopjonnyjon]

Myles, I got my bike back together and ran it for a while this weekend. If anything, the sound is even more pronounced now. I am convinced it is just the the sound of the center kips valve. I think cleaning it really thoroughly made the sound worse.

Sound isn't great with the gopro, but maybe you can make it out.

http://www.youtube.com/v/4qMecD4xvhY

I do recall on our ride though that at least one of your pipe mounts was missing. I replaced the pipe O-rings and all new pipe mounts and springs, but I didn't even realize there was supposed to be a copper gasket in there until I tore it down this winter. Mine was totally pounded out into a paper thin wafer with a few areas totally pounded through. I've got a new one on order, I will let you know what I find when I run it with the new gasket.

I checked out my jetting this weekend. 58 pilot, 168 main. VP110 mixed 50/50 with 91 pump gas, and 40:1 Belray MC1. I've gone a full season without fouling a plug, and it always starts 1st or second kick. Perhaps my seat of the pants isn't calibrated as finely as others, but it seems to always run flawlessly. Do you think Robbie really needs to be rejetting his KTM daily, or is he just doing it because he is looking for something to do?

[Polar-Bus]

I have a buddy with a new 200cc KTM XCW and he basically jets daily...   Just thought I would share that with you guys...

 

Good for him, he spends painstaking amounts of hours chasing the most perfect tune.... no wonder he's so slow...

I have summer jetting and winter jetting, not perfect jetting but safe. No meltdowns, and no fouled plugs. That's good enough for me.